A hot melt adhesive comprising a polyester resin may be used for forming a hot melt adhesive layer for heat sealing and preparing a heat transfer label on a substrate such as a film, a fabric, and paper.
A hot melt adhesive comprising such a polyester resin is, for example, melted, applied on an appropriate substrate, and then cooled to form a hot melt adhesive layer made from a solidified product of the hot melt adhesive on the substrate (See Patent Literature 1).
In order to apply the hot melt adhesive, equipment for melting the hot melt adhesive by high temperature heating and equipment for cooling the high-temperature hot melt adhesive are needed.
Since equipment such as above mentioned is not needed for a hot melt adhesive solution obtained by dispersing a hot melt adhesive in a solvent, equipment for applying the hot melt adhesive solution can be simplified and also efficiency of an application step can be improved.
However, when preparing the hot melt adhesive solution by dissolving or dispersing a polyester resin in the solvent, keeping stable solubility or dispersibility of the polyester resin is difficult. Hence, the polyester resin in the hot melt adhesive solution may flocculate at normal temperature or the hot melt adhesive solution may gel, leading to low preservation stability of the hot melt adhesive solution.
Also, depending on a use, but generally, adhesiveness of a hot melt layer formed from a hot melt adhesive is preferred to be low at normal temperature. There has not yet been provided a hot melt adhesive solution which can form a hot melt adhesive layer with low adhesiveness at normal temperature but nevertheless contains a polyester resin with high solubility or dispersibility in a solvent.